Mold plug



P 1964 w. c. MELLOTT ETAL 3,146,504

MOLD PLUG Filed Feb. 12, 1962 //A/GOT MOL D 16 REF/PAC 7-way INVENTORSW/LZ/S C. MELLOTT; (419A 4. WOLESLAGLE United States Patent 3,146,504MGLD PLUG Willis C. Mellott, Connellsville, and Carl A. Woleslagle,Uniontown, Pa., assignors to Eureka Fire Brick Works, Mount Braddock,Pa., a corporation of New Jersey Filed Feb. 12, 1962, Ser. No. 172,745 3laims. (Cl. 22148) This invention relates to an improved mold plug foringot molds, especially the big-end-up ingot molds.

In forming steel ingots, molten steel is poured into a cast iron ingotmold, allowed to solidify therein, and thereafter removed as a unitarymass by inserting an expulsion element through a bottom opening in theingot mold. The bottom opening is closed during the actual pouring ofmolten steel by means of a mold plug which is formed to fit tightly intothe opening. Each mold plug has a single usei.e., for the pouring of asingle ingot of steel. The ingot mold itself may be utilized for thepouring of many ingots, as many as forty ingots being considered asatisfactory life expectancy for an ingot mold.

Mold deterioration is greatest in the bottom regions of the ingot moldabove the mold plug and results from the splashing of the initial moietyof molten steel against the mold plug and thence against the inner wallsof the ingot mold. The very hot molten steel impinges against therelatively cool cast iron bottom and side walls of the ingot mold andquickly causes deterioration of the ingot mold walls through erosion andthermal shock. The undesirable splashing also causes rapidsolidification of the splashed steel moiety with an accompanyingsegregation of its components with the result that the metallurgicalcomposition of the resulting ingot becomes non-uniform. The solidifiedparticles of cooled steel on the bottom and side walls create what isknown as a scabby ingot surface. The embedded solidified particles ofsplashed steel must be ground off the ingot before the remaining steelof the ingot can be processed.

According to the present invention, a mold plug is provided for ingotmolds which appears to minimize the splashing of the initial moiety ofmolten steel entering into the ingot molds. The results of using thepresent mold plug are:

An increased life of the ingot mold by twenty percent or more, i.e.,each ingot mold can be used to produce about forty-eight ingots ratherthan merely forty ingots as heretofor obtained;

The metallurgical segregation in the resulting ingot is significantlydecreased. Formation of scabby ingot surfaces is minimized.

Thus the principal object of this invention is to provide a mold plugfor a big-end-up ingot mold which will decrease the deterioration of theingot mold and improve the metallurgical quality of the resulting ingot.

This objective is accomplished by providing a novel surfaceconfiguration in the upper surface of the mold plug which includes:

A central spherical-surfaced portion;

An intermediate annular toroidal portion; and

A peripheral rim portion.

The top of the spherical central portion is disposed beneath ahorizontal plane of the peripheral rim portion and the intermediateannular toroidal portion comprises an annular depression ofsemi-circular cross-section.

The invention will be understood by reference to the following detaileddescription and the accompanying drawings in which:

FIGURE 1 is a cross-section illustration of a typical big-end-up ingotmold having a hot-top affixed at its top and a mold plug of thisinvention secured in its bottom opening;

FIGURE 2 is a cross-section illustration of the present mold plug; and

FIGURES 3 and 4 are cross-section illustrations of typical mold plugsheretofor employed in ingot molds.

Referring to FIGURE 1 there is a cast iron ingot mold 10 whichcustomarily has slightly tapering side-walls 11 which join with a bottomwall 12 which has a central opening 13 having the configuration of aconical frustum. A hot-top 14 is fitted over the upper end of the ingotmold 10 under normal circumstances. The hot-top 14 has a central opening15 which is positioned vertically above the bottom opening 13.

A mold plug 16 of conical frustum configuration is placed in the bottomopening 13 to plug that opening against egress of molten steel duringthe pouring of the ingot. Mold plugs normally are formed from cast iron,ceramic materials and graphite. The present mold plug may be fabricatedfrom any of those materials.

An ingot expulsion element (not shown) is rammed against the mold plug16 after the ingot has solidified in order to discharge the ingot andmold plug from the ingot mold 10. The mold plug 16 is discarded after asingle use.

Heretofor mold plugs have had upper surfaces as shown in FIGURES 3 and 4(as well as other configurations) wherein the upper surface 17 of themold plug 16a is fiat (FIGURE 3) and the upper surface 18 of the moldplug 16b (FIGURE 4) is concave.

When mold plugs of the type shown in FIGURES 3 and 4 have been employed,the ingot mold 10 experiences severe deterioration in the regionindicated by the arrows A as a result of splashing of molten steelagainst the relatively cool bottom walls 12 and the lower portion of theside walls 11.

The present mold plug 16, as seen in FIGURE 2, has a circular upper rim19, a circular lower rim 20 and conically tapered side walls 21. Theupper surface includes a central portion 22 and a rim portion 23separated by an intermediate annular portion 24.

It will be observed that the central portion 22 has the cross-section ofa spherical surface having its center at the point B. The intermediateannular portion 24 has a toroidal surface having a circular-arccross-section which has its circular center locus along the horizontalcircle represented by the points C in FIGURE 2. The uppermost portion ofthe central portion 22 (identified by the letter D in FIGURE 2) isdisposed beneath a horizontal plane represented by the letter E. The areof the toroidal intermediate annular portion 24 is tangential to thespherical surface of the central portion 22. The horizontal circle whichdefines the toroidal intermediate annular portion 24 (indicated by thepoints C) likewise is disposed beneath the horizontal plane E.

From the foregoing description, it will be apparent that a conical sidewall portion 25 is provided which joins the circular rim 20 with theintermediate annular portion 24 and which is tangential to the toroidalsurface thereof.

If desired, one or more slots 26 may be provided within the body of themold plug 16 to facilitate stripping of the mold in the manner describedin US. Patents 2,444,- 140, 2,798,268 and 3,008,203. The mold-strippingslots 26 may be cut in the central portion 22 or in the intermediateannular portion 24 i.e., they may communicate with the upper surface ofthe mold plug 16 anywhere within the circular rim 20.

By virtue of the widespread use of hot-tops, the pouring of molten steelis substantially at the direct center of the ingot molds because of therelatively narrow opening 15 in the hot-top 14. Hence the liquid metaldescends in a relatively narrow stream directly against the centerportion 22 of the present mold plug 16. It is postulated that thesplashing which occurs is directed upwardly against the descendingstream of molten metal rather than against the side walls 12 in theregion indicated by the arrows A as heretofor encountered. Thecontrolled splashing pattern appears to result from the use of thepresent mold plug as will be apparent from the following description ofresults.

Examples The operating results achieved through the use of the presentmold plug are quite significant.

The use of the present mold plug (as opposed to the use of a prior artplug of the type shown in FIGURES 3 and 4) increased the life of ingotmolds by more than twenty percent in a series of actual commercialoperations with stainless steel. In all of the described commercialoperations, hot-tops were employed so that the molten metal was pouredinto the ingot molds at precisely the center thereof. Throughout thecommercial operations which have been described, the ingot molds wereinspected at intervals to observe the surface condition.

Through fourteen heats there was no detectable difierence in the ingotmold surfaces. Thereafter the ingot molds which utilized the prior-artmold plugs started to wash out and to develop fire-checks.

After thirty heats had been poured in the ingot molds, there was aconsiderable difference in the condition of the bottom portions of theingot molds.

After forty heats, the ingot molds utilizing the present mold plugs wereonly slightly washed out and exhibited only very light fire checks. Incontrast, the ingot molds which utilized the prior-art mold plugs werebadly washed out after forty heats and had developed heavy fire-checksover their bottom portions. Those ingot molds were discarded after fortyheats. When an ingot-mold is badly washed-out in its bottom portion, theremoval of the solidified ingot becomes troublesome. Throughout theseries of commercial operations, the ingots made in those ingot moldshaving the present mold plugs were removed with no difficulty.

The ingot molds utilizing the present mold plugs continued in servicethrough forty-eight heats and were considered at that time to be stillin condition for additional use.

According to the provisions of the patent statutes, we have explainedthe principle, preferred construction, and mode of operation of ourinvention and have illustrated and described what we now consider to beits best embodiment. However, we desire to have it understood that,within the scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

We claim:

1. An improved plug for a big-end-up ingot mold adapted for insertioninto the base of said mold for closing the lower opening thereof, saidmold plug having a circular upper rim and a circular lower rim and beingin the form of a conical frustum, the upper surface of said mold plughaving a spherical central portion, an intermediate toroidal annularportion and a circular rim portion, the said central portion beingdisposed beneath the said rim portion, and the said intermediate annularportion comprising a circular depression.

2. An improved mold plug for a big-end-up ingot mold adapted forinsertion into the base thereof for closing the lower opening thereof,said mold plug having a circular upper rim and a circular lower rim andbeing in the form of a conical frustum,

the upper surface of the said mold plug having a circular rim portion,

a central portion of spherical outer surface, the highest point of whichis disposed beneath a horizontal plane defined by said outer circularrim portion, and

an intermediate annular portion of toroidal outer surface, the saidtoroidal outer surface being tangential with the said spherical outersurface, and

a conical side wall extending from the said upper circular rim portionand being tangential with the said toroidal outer surface.

3. The mold plug of claim 2 wherein at least one slot is provided withinthe body of the said mold plug communicating with the upper surface ofthe said mold plug within the outer circular rim portion.

References Cited in the file of this patent UNITED STATES PATENTS107,766 Dunfee Sept. 27, 1870 2,113,445 Estep Apr. 5, 1938 2,444,140Messler June 29, 1948 2,572,754 Patterson Oct. 23, 1951 2,798,268Whitacre July 9, 1957 2,863,189 Beck Dec. 9, 1958 3,008,203 DagenhardNov. 14, 1961

1. AN IMPROVED PLUG FOR A BIG-END-UP INGOT MOLD ADAPTED FOR INSERTIONINTO THE BASE OF SAID MOLD FOR CLOSING THE LOWER OPENING THEREOF, SAIDMOLD PLUG HAVING A CIRCULAR UPPER RIM AND A CIRCULAR LOWER RIM AND BEINGIN THE FORM OF A CONICAL FRUSTUM, THE UPPER SURFACE OF SAID MOLD PLUGHAVING A SPHERICAL CENTRAL PORTION, AN INTERMEDIATE TOROIDAL ANNULARPORTION AND A CIRCULAR RIM PORTION, THE SAID CENTRAL PORTION BEINGDISPOSED BENEATH THE SAID RIM PORTION, AND THE SAID INTERMEDIATE ANNULARPORTION COMPRISING A CIRCULAR DEPRESSION.